(Original post by SashaLuLu)
ionic bonds are always stronger than covalent bonds. this is due to the strong electrostatic forces between oppositely charged ions. It is easier to break the covalent bonds. It will only be incredulity strong if it is macromolecular. Silicon dioxide is macromolecular.

not always, Na2O is giant ionic, ionic bonds need to be broken to melt it, but it has lower melting point than SiO2 which is a macromolecular, which needs many covalent bonds to be broken.